1. Field of the Invention
The present invention relates to a waferless clean process and, more particularly to a waferless automatic clean process for cleaning a reaction chamber of dry etchers in semiconductor manufacturing processes.
2. Description of the Related Art
Many conventional etching machines cause byproducts to deposit on the surfaces of the reaction chamber to form particles. The particles will contaminate a wafer being produced and thus a defection wafer is produced. Thus, after a period of production, wet cleaning the chamber by a chemical solution is necessary. However, wet cleaning the chamber is time-consuming. To overcome this problem, a periodic plasma cleaning is usually used for cleaning the chamber and may extend MTBC (Mean Time Between Wet Clean).
The conventional plasma cleaning method includes: after a wafer produced in a reaction chamber, transporting the wafer from the reaction chamber to a loading dock; unloading the wafer from the loading dock by an operator; loading a plasma cleaning and seasoning dummy wafer to the loading dock by the operator and then to the chamber; plasma cleaning and seasoning the chamber, unloading the plasma cleaning and seasoning wafer from the chamber to the loading dock; unloading the plasma cleaning and seasoning wafer from the loading dock by the operator; and loading a monitoring wafer to the loading dock by the operator and then to the chamber.
The shortcomings of the conventional plasma cleaning method are:
a) The production of wafers is interrupted by an operator in order to perform the plasma cleaning, and thus downtime of the etcher is increased and the throughput is decreased. PA1 b) Oxide wafers are used for cleaning, and blanket Si or poly dummy wafers are used for seasoning. The silicon of the dummy wafer will react with the fluoride to produce a gaseous silicon fluoride (SiFx) to be dissipated and driven off by a pump, so that the reaction chamber is restored to the initial process conditions. Therefore, extra loading of providing oxide wafers, silicon wafers and poly wafers is imposed on a thin film module. Consequently, the cost is increased. PA1 c) The MTBC is increased from 2000 RF minutes to 8000 RF minutes only (RF minutes stand for the time spent by a radio coil or the operation time of plasma cleaning). PA1 After production of a batch of wafers is finished, the wafers are removed out of the chamber to the loading dock. Meanwhile the etcher automatically starts waferless plasma cleaning. The operator unloads the wafers and then loads monitoring wafers to the loading dock. After cleaning, the monitoring wafers are loaded into the chamber immediately.
The present invention provides a plasma cleaning method for a dry etcher without dummy wafers so as to overcome the above-mentioned disadvantages.